Stack vs Heap

 Stack

• Keeps track what is executing or what's been called
   

• Keeps everything in series of boxes one on top of the next
   

• We can use only the top box content
   

• When we are finished with the top box we throw it away
   

• The stack is self-maintaining

 Heap

 Stack vs Heap

 Stack

 Heap

Garbage Collector

 Garbage collector

• Unfortunately memory is not infinite
   

• Manage it:

  • ​Manually

  • Automatically (Garbage Collector)
    ​

• ​Manages the Heap memory

 Garbage collector

Understanding .NET Garbage Collection

 Garbage Collector

• Every object holds memory in the manged heap
   

• The garbage collector is called periodically
   

• If there are no direct or indirect references the GC frees the memory from the object
   

• GC compacts the heap

Reference vs Value Types

 Value types

• bool
• byte
• char
• decimal
• double
• enum
• float

• int
• long
• sbyte
• short
• struct
• uint
• ulong
• ushort

• System.ValueType

public static void Main()
{
    int x = 5;
    int y = 30;

    bool isBigger = x > y;
}

 Value types

 Stack

public int ReturnValue()
{
    int x = 3;
    int y = x;
    y = 4;
    return x;
}

x | int = 3

y | int = 4

• If we call the method it will return the value 3
   
• These are all value types and are held in the Stack (not always)
  • ​In method declaration they are held in the Stack
     
  • If they are declared in a reference type they are held in the Heap

 Reference types

• class
• interface
• delegate
• object
• string

• System.Object

// The class is Reference type
public class Program
{
    static void Main()
    {
        // The list is Reference type
        List<int> list = new List<int>() { 1, 2, 3 };
        
        // The string is Reference type
        string a = "Pesho";
    }
}

 Reference types

public int ReturnValue()
{
    MyInt x = new MyInt();
    x.Value = 3;
    MyInt y = x;
    y.Value = 4;
    return x.Value;
}

• If we call the method it will return the value 4
   
• MyInt is a class (reference type​)
   
• Reference types are always held in the Heap

 Stack

Heap

y | POINTER

x | POINTER

Myint

Value | int

Additional Materials

 Additional Materials

• ​C# Heap(ing) Vs Stack(ing) in .NET: Part I
   
• Fundamentals of Garbage Collection
   
• The Truth About Value Types
   
• Six important .NET concepts